1. Field of the Invention
The present invention relates to the authentication method of an electronic tag attached to a goods, more particularly to provide an electronic tag authentication device capable of improving the authentication accuracy of an electronic tag and reducing interference with another electronic tag authentication device by changing the directivity of the antenna of the relevant electronic tag authentication device and a communication adjustment method with the electronic tag.
2. Description of the Related Art
Recently, in the fields of production and distribution, attention has been focused on a radio frequency identification (RFID) method as the management system of components or inventory. For example, if a different reader/writer is used for each showcase to manage goods with an electronic tags in a showcase, using such RFID, it causes a problem that the authentication accuracy of a tag degrades due to interference with another reader/writer or the like, although it depends on the disposition way of showcases.
As the prior arts concerning the data reading of such an electronic tag and an IC card, there are the following references.    Patent reference 1: Japanese Published Patent Application No. 2000-242742 “Interrogator System”    Patent reference 2: Japanese Published Patent Application No. 2003-283367 “Interrogator System”
Each of these references discloses a system interrogating a moving IC card, using a plurality of readers/writers. Patent Reference 1 discloses a technology for preventing the interference of a transmission signal between readers/writers by transmitting an interrogation signal when one reader/writer detects that a radio transmission signal from the other reader/writer is in a no-signal state.
Patent Reference 2 discloses a system for preventing interference caused when one reader/writer receives a transmission signal from the other reader/writer while expanding a communicable area, by overlapping and setting the communicable area of each of antennas corresponding to a plurality of readers/writers and synchronizing the transmission/reception of the plurality of reader/writers.
However, in the technology of Patent Reference 1, a plurality of readers/writers cannot be simultaneously operated. In order to solve the problem of the present invention aims to solve, a communicable area must be rather restricted. The technology of Patent Reference 2 cannot also be applied.